Part of: Clear language
Last updated: 25 February, 2020
Following this helps people with:
time pressures: simply written content is easier to scan and absorb
stress: when anxious it's harder to comprehend things
multi-tasking: it's harder to comprehend convoluted content
cognitive impairments: simple sentences carry less cognitive load
visual impairments: clear, concise copy is shorter to read
motor impairments: clear, concise content needs less navigation
Short, simple sentences are better on the web than long, protracted prose with complex syntax.
WCAG says: "using the clearest and simplest language appropriate is highly desirable."
The maximum sentence length for a good level of comprehension is 25 words. Split long sentences up into 2 or 3, or use bullet points.
Oxford Guide to plain English, GOV.UK and linguists agree:
15 word sentences are more likely to be comprehensible
25 words is a good maximum sentence length limit
above 40 words sentences are hard to comprehend easily
"This sentence is about 15 words long and is easy to understand."
A mix of slightly shorter and sightly longer sentences can make reading more interesting.
They are less easy to comprehend quickly. Understanding them requires more cognitive effort than simple sentences.
Complexity depends on:
number of clauses in a sentence, the more clauses the more complex it is
distribution of associated words across the sentence – how easily can the brain 'parse a phrase': recognise, connect and comprehend words that together convey meaning
"The red fox jumped over the gate." – easier to understand
"The fox, which was red, over the gate jumped." – harder to understand
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Writing for GOV.UK, UK Government website
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Reading Level, Understanding SC 3.1.5, WCAG, 2008
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Text complexity, ATOS, and Lexile® Measures, Renaissance Learning, 2016
'Understanding Plain English summaries. A comparison of two approaches to improve the quality of Plain English summaries in research reports.' E. Kirkpatrick, W. Gaisford, E. Williams, E. Brindley, D. Tembo, D. Wright, 2017
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The Crystal Mark standard Plain English Campaign. Undated.